<!DOCTYPE html>
<html lang="en" xmlns:th="https://www.thymeleaf.org/">
<head>
    <meta charset="UTF-8">
    <title>pdf</title>
</head>
<body>
show a pdf
    <p th:text="${url}"></p>
    <input name="pdf" id="pdf" type="button" value="show a pdf" onclick="showPdf()">
</body>

<script>
    function showPdf() {
        window.open("/pdf/show");
    }
</script>
</html>